I don't know the rules for the US, but for Canada the rules are easy.
If the car does not have a Canadian or US compliance label, then you can import any car you want as long as it is 15 years old to the month and older (not newer!)

Importing from the US - follow this link:
www.riv.ca

Importing anywhere else - follow this link:
http://www.tc.gc.ca/roadsafety/importation/menu.htm

Last but not least, here is a sie with some very informative people that may be able to help you:
http://www.ivoac.ca/pn/

Good Luck!

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1989 300CE Astralsilber/Schwarz
1992 300CE Schwarz/Schwarz